Question

State Faraday's first law of electrolysis.
Write any 'two' uses of each of the following
(a) $H_{2}S{O}_4$, (b) Chlorine
Distinguish between crystalline solids and amorphous solids.
A solution of a substance having mass $1.8\times {10}^{-3}kg$ has the osmotic pressure of 0.52 atm at 280 K. Calculate the molar mass of the substance used.
[Volume $=1d{m}^3,R=8.314J{K}^{-1}mo{l}^{-1}$]

Answer 1

Faraday's first law of electrolysis
Amount of substance that undergoes oxidation or reduction at each electrode during electrolysis is directly proportional to the amount of electricity that passes through the cell.
Mathematically:
$\text{Moles of substance produced}=\frac{\text{I(A)}\times \text{t(s)}}{\text{96500 C/mol}{e}^{-}}\times \text{mole ratio from stoichiometry}$
$\text{Mass of substance produced}=\frac{\text{I(A)}\times \text{t(s)}}{\text{96500 C/mol}{e}^{-}}\times \text{mole ratio}\times \text{molar mass of substance}$
Uses:
(a)
$H_{2}S{O}_4$
(i) It is commonly used as laboratory agent.
(ii) It is dehydrating agent.
(b) Chlorine
(i) as bleaching agent in textile and paper industry.
(ii) for sterilization of municipal supply water.
Distinction between crystalline solids and amorphous solids.

Crystalline solids	Amorphous solids
They are homogeneous with definite repeating pattern of constituent particles.	They are non homogeneous and do not have well developed perfectly ordered crystalline structure.
They are anisotropic	They are isotropic

Calculation for the molar mass of the substance:

$M_2=\frac{W_2}{\Pi }\frac{RT}{V}$
Here, $M_2$ is the molar mass of solute, $W_2$ is the mass of solute, $\Pi$ is the osmotic pressure, R is the ideal gas constant, T is the absolute temperature and V is the volume.
$M_2=\frac{1.8\times {10}^{-3}kg}{0.52atm}\frac{0.0821d{m}^{3}atm/mol/K\times 280K}{1d{m}^3}$
$M_2=0.0796kg/mol=79.6g/mol$